Technically, I'd say it's flying if the main upward force is lift, and swimming if the main upward force is buoyancy. And while it's often pointed out that sha

Technically, I'd say it's flying if the main upward force is lift, and swimming if the main upward force is buoyancy. And while it's often pointed out that sharks have negative buoyancy and have to sink or swim, they're only slightly denser than water, and some species are positively buoyant: https://www.sciencedaily.com/releases/2015/06/150619103518.htm https://www.sciencedaily.com/releases/2015/06/150619103518.h...